Configuring Link Aggregation; Understanding Port Trunk Groups - D-Link DES-6500 User Manual

D-Link DES-6500 Layer 3 Stackable Gigabit Ethernet Switch

Configuring Link Aggregation

Understanding Port Trunk Groups

Port trunk groups are used to combine a number of ports together to make a single high-
bandwidth data pipeline.
The Switch treats all ports in a trunk group as a single port. Data transmitted to a specific host
(destination address) will always be transmitted over the same port in a trunk group. This
allows packets in a data stream to arrive in the same order they were sent.
Link aggregation allows several ports to be grouped together and to act as a single link. This
gives a bandwidth that is a multiple of a single link's bandwidth.
Link aggregation is most commonly used to link a bandwidth intensive network device or
devices, such as a server, to the backbone of a network.
All ports in the group must be a member of the same VLAN and their STP status
configuration, static multicast entries, traffic control, traffic segmentation and 802.1p default
priority, must be identical. Also, port locking, port mirroring and 802.1X must not be enabled
on the trunk group. Further, the aggregated links must all be of the same speed and should be
configured as full-duplex.
The Master Port of the group, becomes the configuration for all of the ports in the aggregation
group and all configuration options, including the VLAN configuration, that can be applied to
the Master Port are applied to the entire link aggregation group.
Load balancing is automatically applied to the ports in the aggregated group, and a link failure
within the group causes the network traffic to be directed to the remaining links in the group.
The Spanning Tree Protocol will treat a link aggregation group as a single link, on the switch
level. On the port level, the STP will use the port parameters of the Master Port in the
calculation of port cost and in determining the state of the link aggregation group. If two
redundant link aggregation groups are configured on the switch, STP will block one entire
group, in the same way STP will block a single port that has a redundant link.
To configure port trunking, click on the Link Aggregation hyperlink in the Configuration
folder to bring up the Current Link Aggregation Group Entries table:
NOTE: You cannot mirror a fast port onto a slower port. For
example, if you try to mirror the traffic from a 100 Mbps port onto a
10 Mbps port, this can cause throughput problems. The port you are
copying frames from should always support an equal or lower speed
than the port to which you are sending the copies. Also, the target
port for the mirroring cannot be a member of a trunk group. Please
note a target port and a source port cannot be the same port.
Note: If ports become disconnected within a trunk group,
intended packets will be load shared to the other up-linked
ports of the link aggregation group.
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